I was just listening to a tape I made of the Portland 2002 soundcheck, and noticed that Thurston keeps jamming on a riff that seems reminiscent of Reena (Jim and Steve join in, too). He even says "We'll work on it!" at one point. I remember I actually relistened to the tape after Nurse came out to see if he HAD worked it into something, but now that I hear it again it sounds like the foundation of Reena (to me).
http://members.shaw.ca/silvercircle/maybereena.wma
What do you think?